1. Field of the Invention
The present invention relates to patient interface devices for transporting a gas to and/or from an airway of a user, and, in particular, to an accessory for use with a headgear in a patient interface system for gauging and indicating the current strapping force applied by the headgear.
2. Description of the Related Art
There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube in their esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, which varies with the patient's respiratory cycle, to treat a medical disorder, such as sleep apnea syndrome, in particular, obstructive sleep apnea (OSA), or congestive heart failure.
Non-invasive ventilation and pressure support therapies involve the placement of a patient interface device, which is typically a nasal mask that covers the nose, a nasal/oral mask that covers the nose and mouth, or full face mask that covers the patient face, on the face of a patient. The patient interface device interfaces the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient. It is known to maintain such masks on the face of a wearer by a headgear having upper and lower straps, each having opposite ends threaded through connecting elements provided on the opposite sides and top of a mask. Because such masks are typically worn for an extended period of time, it is important for the headgear to maintain the mask in a tight enough seal against a patient's face without discomfort. One such headgear is disclosed in U.S. Pat. No. 5,517,986, which is assigned to the assignee of the present application, and includes a cap-like headpiece adapted to fit the crown and back of a patient's head and lower straps for providing a two-point connection with a gas delivery mask.
Over tightening of mask headgear straps frequently occurs during therapy such as OSA therapy. Over tightening is undesirable as it typically causes discomfort, facial red marks, pressure sores and/or open wounds. As a result, over tightening can have a tremendously negative effect on compliance with therapy as patients will be reluctant to use the mask as often and/or for as long as directed. The importance of therapy compliance is increasing, as insurance and Medicare guidelines are now requiring the industry to prove compliance for their patient populations.
In the clinical setting, an experienced technician or therapist may be knowledgeable enough to avoid unnecessary over tightening. However, it is often the case that even such experienced caregivers over tighten headgear and/or directly or indirectly instruct the patient to over tighten in order to ensure that a good seal is achieved so that therapy, such as CPAP therapy, is delivered.
In addition, as mask designs evolve, the amount of strapping force needed to obtain a good seal between the mask and the patient's face often decreases. However, a patient using such a mask may not know or understand that less strapping force (i.e., than was required for prior mask designs) is needed. This lack of understanding may lead to over tightening of the headgear used in conjunction with the mask.
Thus, there is a need for a solution that helps patients to avoid unnecessary over tightening of headgear while at the same time ensuring that proper therapy is delivered.